1. Field of the Invention
The present invention relates to an electrolytic treatment method for manufacturing a planographic printing plate support body in which an aluminum or an aluminum alloy is employed as a support body.
2. Description of Related Art
In general, in order to use an aluminum plate as a support element of a planographic printing plate, it is required to have appropriate adhesive properties to a photosensitive material and water preserving properties, and further, make the plate uniformly surface-roughened. Being uniformly surface-roughened means that the sizes of produced pits are appropriately equal, and requires that such pits are uniformly produced on their full faces. In addition, the pits considerably influence dirt retardant properties, printing resistance or the like that are printing performances of a printing plate material, and its quantity is an important factor for making a printing plate. Further, in recent years, a computer system for direct plate making from digital signals or the like is becoming popular with advancement of information system. In particular, with advancement of miniaturization and high yielding of solid laser and semiconductor laser beams, such computer system is becoming rapidly popular. It is also anticipated that a planographic printing plate support element restricts laser beam halation, and provides water preserving properties, hydrophilicity, printing resistance, and dirt retardant properties which are important for a printing plate.
As a recording material for infrared-ray laser beams, in Japanese Patent Publication No. 61-48418, there is disclosed an anodic oxidation support element having at least an oxide layer of 5 to 12 g/m2. In addition, in Japanese Patent Laid-Open No. 63-260491, there is proposed a surface-roughened and anode-oxidized support element in which a sol having a nuclei to be reduced to a silver complex is adhered. In U.S. Pat. No. 4,555,475, there is proposed a support element silicate-treated on a surface having an anodic oxidation skin film to form a silicate of aluminum of 2 to 8 mg/m2. In EP 164128B also, there is proposed a method for graining an aluminum surface, anodic oxidation, causing silicate treatment, applying a carbon black to make a photosensitive material, thereby forming an image. Further, in Japanese Patent Laid-Open No. 10-228992, there is proposed a support element for restricting halation. All of the patents assume a uniform rough surface. Such rough surface is made by mechanical surface-roughening method, electrochemical surface-roughening method, chemical etching technique or the like. Among them, the quality of the printing plate material is greatly influenced by electrochemical surface-roughening. It is an important task to make a high quality rough surface and to establish a production method having its stable mass productivity.
For example, the inventor et al. have proposed in Japanese Patent No. 2660582 that circuits for an auxiliary electrode are coupled with circuits connected to a main opposite electrode in parallel; a mechanism consisting of a diode-like action such as diode or thyristor for controlling the flow in the main opposite electrode of an anode current is provided at a power source or the circuits for the auxiliary opposite electrode; phase angle control is applied by each mechanism according to a phase angle of a waveform generated at the power source, and a control branch current is supplied.
In addition, in Japanese Patent No. 2581954, it is proposed that a sintered body containing magnetic iron oxide is employed for the auxiliary opposite electrode.
However, although the inventions of Japanese Patent Nos. 2660582 and 2581954 are superior inventions, it is required to provide an electrolytic treatment method for manufacturing a planographic printing plate support body capable of more uniform surface-roughening and maintaining a predetermined rough surface with recent advancement of direct laser output.
It is an object of the present invention to provide an electrolytic treatment method for manufacturing a planographic printing plate support body capable of more uniform surface-roughening and maintaining a predetermined rough surface.
In order to achieve the foregoing object, according to the present invention, there is provided an electrolytic treatment method for electrolytic treatment of a target material by liquid electric power supply using an alternating waveform current in an electrolytic treatment solution consisting essentially of nitric acids or hydrochloric acids existing in an electrolytic jar, the electrolytic treatment method being characterized in that the electrolytic jar is divided into two sections; electrodes installed in the divided electrolytic jar are defined as a main opposite electrode and an auxiliary opposite electrode installed in their respective different sections of the electrolytic jar; and an electricity quantity of the auxiliary opposite electrode is set in the range of 0.5% to 9% of a total electricity amount of the opposite electrode. In addition, the current supplied to the auxiliary opposite electrode can be supplied to the main opposite electrode and the auxiliary opposite electrode using a single electric source by constructing a circuit so as to supply the current to the auxiliary electrode by controlling a phase angle of the waveform generated by an alternating waveform power source.
Further, according to the present invention, a resistance value of a support member for supporting a target material is set to at least 0.01 Mxcexa9.
Furthermore, according to the present invention, the frequency of the alternating waveform current is set in the range of 50 to 80 Hz, and the current density of the main opposite electrode is set in the range of 5 to 50 A/dm2.